"Grade repetition" (sometimes referred to as ''grade retention") occurs when students are held in the same grade for an extra year rather than being promoted to a higher grade along with their age peers. In some school systems grade repetition is seen as a valid corrective action that should be taken in cases of academic failure. In other school systems grade repetition is not permitted, and instead the policy for all pupils is "social promotion" whereby students pass automatically to the next grade with their peers and - if required - receive remedial academic assistance. The booklet takes a close look at the issues surrounding the implementation and effects of grade repetition. This analysis commences with an examination of the five major reasons for the decision to repeat and the sources of that decision (students, families, and schools). The author also points out that the reasons for applying grade repetition often differ across developed and developing countries. The booklet then moves on to examine the effects of grade repetition along three important dimensions: (a) the effects on academic achievement - where research has indicated short-term gains and long-term problems because grade-repeaters eventually fall further behind; (b) the effects on student self-esteem, peer relationships, and attitudes towards school - with negative outcomes in these areas leading to increased risks of dropping out; and (c) the effects on school operations - whereby high levels of grade repetition can lead to increased class sizes and classroom management problems (due to large age differences among pupils in the same classroom). The overall conclusions of the booklet suggest that that the application of grade repetition brings extra costs and long-term negative academic and social consequences.